The present invention relates to formulations which essentially comprise a film-former or casting resin and a silanized pearl lustre pigment.
In the case of metal effect pigments, in terms of their applications characteristics, there are various types of pigments, namely the so-called leafing and non-leafing types.
Leafing refers to the floating or accumulation and the orientation of pigments at the surface of a coating substance or of a coating. Under the effect of the interfacial tension between pigment and coating composition, the lamellar pigment particles move to the surface of the coating composition where they come together to form a continuous film. The visual impression given is of a closed metallic surface of high reflectivity with a silvery-bright metallic gleam. The phenomenon of leafing has previously only been observed for metal effect pigments.
In the case of pearl lustre pigments based on mica, the only pigments known so far are those with non-leafing properties; in other words, pearl lustre pigments exhibit, in virtually all those areas in which they are used, a non-leafing behaviour, i.e. a good compatibility with the medium surrounding them: the individual pigment particles are completely wetted and distributed in the medium in which they are embedded.
However, in some areas of application, in particular those in which the orientation of pearl lustre pigments is incomplete, such as film-formers, powder coatings and casting resins, a leafing behaviour is very often desirable.
The object was therefore to discover formulations which contain pearl lustre pigment and in which a leafing effect is observed.
It has now been found that, surprisingly, pearl lustre pigments which have been coated with a silane, with the aim of achieving improved compatibility, exhibit a pronounced leafing behaviour in film-formers and casting resins. In the formulation, leafing leads to a significantly improved orientation of the pigments at the surface, resulting in an increased pearl lustre.
The invention therefore relates to formulations essentially comprising a film-former or casting resin, characterized in that they contain pearl lustre pigments which are coated with one or more silanes of the formula I
SiR1R2R3R4xe2x80x83xe2x80x83I
in which
R1 and/or R2 are alkyl having from 1-30 carbon atoms, in which one or two non-adjacent CH2 groups may also be replaced by xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94 or xe2x80x94OCOxe2x80x94, and the remaining radicals R1-4 independently of one another are halogen or alkoxy having from 1-20 carbon atoms, in which one or two non-adjacent Cal groups may also be replaced by xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94 or xe2x80x94OCOxe2x80x94.
Pigments coated with a silane of the formula I are already known from EP 0,492,223. The pigments it describes are used for inhibiting yellowing in plastics.
This document, however, does not describe the combination of silanized pearl lustre pigment and film-former or casting resin for achieving a leafing effect.
An essential constituent of the formulation according to the invention is the silanized pearl lustre pigment. All conventional pearl lustre pigments can be used as the base pigment, for example mica or silicate flakes coated with coloured or colourless metal oxides such as TiO2, Fe2O3, SnO2, Cr2O3, ZnO and other metal oxides, alone or as a mixture in a single layer or in successive layers. These pigments are known from, for example, the German Patents and Patent Applications 14 57 468, 19 59 998, 20 09 566, 22 14 545, 22 15 191, 22 44 298, 23 13 331, 25 22 572, 31 37 808, 31 37 809, 31 51 343, 31 51 354, 31 51 355, 32 11 602 and 32 35 017 and are commercially available, for example under the tradename Iriodine(copyright) from E. Merck, Darmstadt.
The silanization of the pearl lustre pigments is carried out as described in EP 0,492,223. The silanized pearl lustre pigments preferably used are pigments, in particular TiO2-coated mica pigments, which are coated with a silane or silane mixture of the formula I SiR1R2R3R4, in which the radicals R1-4 have the following meanings:
R1 and/or R2 are alkyl having from 1-30 carbon atoms, and in particular 10-30 carbon atoms, in which one or two non-adjacent CH2 groups may also be replaced by xe2x80x94CHxe2x95x90CHxe2x80x94 and/or xe2x80x94Oxe2x80x94. Particular preference is given to decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosanyl, heneicosanyl, docosanyl, tricosanyl, tetracosanyl, pentacosanyl, hexacosanyl, heptacosanyl, octacosanyl, nonacosanyl, triacontanyl, 12,12-dimethyltetradecyl, 11-propyl-12-butylpentadecyl and 8,8-dimethyl-12-propyl-13-propylhexadecyl radicals.
the remaining radicals R1-4 are halogen or alkoxy having from 1-20 carbon atoms, in particular 1-10 carbon atoms, in which one or two non-adjacent CH2 groups may also be replaced by xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94 or xe2x80x94OCOxe2x80x94. Particular preference is given to fluoro, chloro, methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, nonyloxy or decyloxy radicals.
The pearl lustre pigments which are particularly preferably used are coated with a silane or silane mixture of the formula IA
(CnH2n+1)Si(OCmH2m+1) 3xe2x80x83xe2x80x83IA
in which n is 1-30 and
m is 1-10. The silane mixture preferably consists of two or three silanes of formula I or IA.
All conventional casting resins, for example gel coats, and film-forming systems are suitable for the formulation according to the invention. The term film-forming system should be understood here as meaning all solvent-containing or else solvent-free binder systems with which it is possible, by physical or chemical methods, for example drying at room temperature or at elevated temperatures of up to about 200xc2x0 C., polymerization and/or crosslinking induced by chemical means or by radiation, for example TV radiation, and other conventional treatment methods, to form smooth and readily adhering films. It is preferred to use high-solids film-formers, UV- and electron beam-curing film-formers and, in particular, powder coatings.
The production of the formulation is simple and easy to manage. The silanized pearl lustre pigment is stirred, with or without the addition of solvent, into the film-former or into the casting resin and mixed intensively (for example with a modified dissolver). The formulation is then applied (for example by brushing, dipping, spraying or electrostatically) to the substrate material to be coated, so that the substrate surface is fully covered with a. homogeneous film. Finally the coating is fully cured under the conventional conditions. Due to the leafing effect a coating of pronounced pearl lustre is obtained in which the pearl lustre pigment is accumulated at the surface.
The leafing effect, that is the floating of the pearl lustre pigments at the surface of the film-former or the casting resin, and the leafing stabilityxe2x80x94a leafing effect which is unchanged over a prolonged period in the formulationxe2x80x94depend on the film-forming system and on the casting resin used.
The degree of pigmentation, the viscosity and the curing characteristics of the film-former or casting resin may also influence the leafing effect.
For a good leafing effect, the pigmented formulation should not contain more than 15% by weight of pearl lustre pigments. The pigment content is preferably between 0.3-10% and is in particular from 1-5%, based in each case on the binder or resin.
Over the silanized pigments it is also possible to apply, as a top coat, one or more clearcoats, for example an aqueous coating or powder coating, to improve the surface quality; the aim of this as a rule is to achieve a further improvement in both the appearance and the durability of the overall finish. The transparent final coat, however, is not absolutely necessary.
The formulations according to the invention can be applied to any desired substrate materials, for example metals such as iron, steel, aluminium, copper, bronze, brass and metal foils, or else metal-coated surfaces of glass, ceramic and concrete, and also to wood, for example furniture, or clay, paper, packaging materials, for example plastic containers, or films, boards or other materials for decorative and/or protective purposes. The finishes obtained in every case, due to the leafing effect, are highly lustrous and of enhanced reflectivity. Furthermore, due to the compact platelet structure of the individual pigment particles at the surface, a good mechanical and chemical resistance is achieved.
Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.
In the foregoing and in the following examples, all temperatures are set forth uncorrected in degrees Celsius and unless otherwise indicated, all parts and percentages are by weight.
The entire disclosures of all applications, patents and publications, cited above and below, and of corresponding application(s) German P 43 23 914.5, filed Jul. 16, 1993, are hereby incorporated by reference.